A metrial gland (Mg) develops adjacent to the placenta in several species. The function of this tissue and its granulated metrial gland (GMG) cells is unknown, but previous studies have indicated that GMG cells are lymphoid cells. We have demonstrated that GMG cells contain the pore-forming protein, perforin, that is important in the cytotoxicity of natural killer (NK) cells. WE HAVE AlSO SHOWN THAT DISSOCIATED GMG CELL PREPARED BY A NON-ENZYMATIC METHOD BIND TO NK-SUSCEPTIBLE YAC-l CELlS BUT NOT TO NK. RESISTANT THYMUS CElLS. BOTH OBSERVATIONS SUGGEST THAT GMG cells may be NK-like cells, and the experiments proposed here are designed as a further test of this hypothesis. We propose immunolabeling studies to detect NK cell membrane markers and granule proteins in GMG cells, and we will attempt to deplete GMG cells by treatments that deplete NK cells in vivo. We will dissociate MG tissue by ENZYMATIC AND NON-ENZYMATIC METHODS AND OBTAIN FRACTIONS enriched in GMG cells on density gradients. We will then determine the NK activity of the dissociated MG cells in a 51 Cr-release cytotoxicity assay; ASSESS BINDING OF THE ISOLATED GMG CELLS TO A PANEL OF NK- SUSCEPTIBLE AND RESISTANT TARGET CELLS; DETERMINE THE EFFECTS OF IV VITRO CULTURE, LYMPHOKINES, AND PROSTAGlANDINS ON THE ENZYMICALLY DISSOCIATED CELLS; AND IDENTIFY THE SPECIFIC EFFECTOR CELL RESPONSIBLE FOR activity by the use of single-cell cytotoxicity assays. To obtain information about a possible site of functional NK activity by GMG cells in vivo, we will carry out an ultrastructural study to determine whether apoptotic death occurs in labyrinthine cells to which GMG cells are bound. Since NK cells cause apoptotic death in their target cells, apoptosis in these labyrinthine trophoblast cell would suggest that GMG cells may cause NK cytolysis in the labyrinth. Since there are indications that GMG cells may be activated NK cells, we will use immunoloabeling to study regulatory factors that may act locally to influence NK activity, including interferons, interleukin-2, prostaglandins and macrophages. If GMG cells are NK-like cells, they may play an immunoregulatory role in the pregnant uterus, or they may be involved in surveillance against tumor cells. We suspect that the MG represents a host protective immune response whose function is surveillance against aberrant trophoblast or other fetal cells that might otherwise enter the female and proliferate. Our long term objective is a better understanding of the role of the metrial gland during pregnancy. Scientific disciplines involved are reproductive biology, immunology, and cell biology.